The invention relates to a pump assembly for filling various drywall finishing and taping tools with a viscous material. More specifically, the invention relates to a pump assembly having a relief valve with a plurality of relief pressures.
The building trades utilize many different tools for applying pastes, slurries and other viscous liquids, such as drywall compound, tile mastic, roofing asphalt and grout, to name just a few. At some building sites, application tools are connected by tubing, hoses or other conduits to a continuous supply of the viscous liquid, which is typically delivered under pressure. At other building sites, where the operator cannot be confined to the immediate vicinity of a pumping station, application tools are periodically filled with a batch of the viscous liquid.
Taper tools and finishing tools designed to carry a quantity of drywall compound for taping and finishing drywall joints are representative examples of the batch application tools. These tools have traditionally required frequent refilling with a hand-operated piston pump. For example, drywall compound is mixed with a solvent in a bucket or other storage container to produce the desired consistency, and then the cylinder of the hand-operated pump is placed in the bucket. An appropriate adaptor is mounted on an outlet of the hand-operated pump, between the outlet and the tool. The taper tools and the finishing tools are filled by manipulating a handle of the hand-operated pump in an up-and-down motion. One example of a hand-operated pump system is described in U.S. Pat. No. 6,378,738 B1, issued to Speaker et al. Another example is described in U.S. Pat. No. 5,711,462, issued to Hard.
Empirical measurements, using properly mixed compound, reveal that a force in excess of 30 pounds of force must be exerted on the handle of a typical hand-operated pump. This fact, coupled with the position of the handle at the bottom of the down-stroke, usually about 10 inches from the ground, can make for an awkward, tiring and sometimes painful experience as the operators are constantly bending over during fillings.
In order to reduce the strain on the operators, previous pump designers have attempted to develop alternate methods for supplying drywall compound to the tools. For example, one previously disclosed system described in U.S. Pat. No. 5,497,812, issued to Orosco et al., utilizes a reciprocating air cylinder attached directly to the cylinder of an existing hand-operated pump. While these alternate systems are commendable and may reduce operator fatigue to some extent, the alternate systems have not been very well received in the field. Possible reasons that the building trades have been reluctant to adopt these alternate systems include mechanical complexity, lack of compressed air (to power pneumatic cylinders etc.), size, portability, ease of cleanup and/or cost.
Another reason that the building trades have been reluctant to adopt air-powered pumping systems is that various batch application tools require overpressure protection at different pressure relief set points. For example, a taper tool known as the Bazooka(trademark) is commercially available from Ames Tool Corporation, the assignee of the present invention. The Bazooka(trademark) requires a relatively large volume of drywall compound delivered at a comparatively low pressure. In contrast, a finishing tool known as the MudRunner(trademark), also available from Ames Tool Corporation, has a relatively small capacity, but requires a significantly greater fill pressure to overcome the force of an internal gas spring/piston assembly. Test results indicate that the optimal fill pressure for the MudRunner(trademark) is approximately one and one-half times the fill pressure of the Bazooka(trademark). Consequently, any powered pumping assembly used to fill both of these tools must be capable of providing two, distinct pressure relief set points and volumetric relief capacities. Because these tools are routinely used in close proximity to each other at a construction site, building contractors would welcome a pumping system that could serve both.
This need for two or more distinct pressure relief set points is shared by other pairs of batch application tools that might reasonably be expected to be used at the same construction site. A need exists for a simple and reliable powered pumping assembly for filling various tools that does not require a source of compressed air to operate. The new pumping assembly should be rugged, lightweight and easily portable. Building tradesmen should be able to operate the new pumping assembly, without need for any new skills or special training. The new system should provide overpressure protection suitable for more than one type of batch application tool with different pressure requirements.
The invention is a powered pumping system for filling various batch application tools with a viscous material. The system includes a motor mounted on a wheeled frame. The motor drives a slider-crank mechanism attached to a reciprocating displacement pump. Affixed to the pump outlet is a relief valve having a plurality of predetermined relief pressure settings. The relief valve serves as a conduit between the pump and any one of various batch application tools while the tool is being filled with the viscous material.
To initiate pumping, operators connect a filler port of the tool to a relief valve outlet and actuate a switch, such as a foot pedal. The relief valve of the present invention automatically selects a relief pressure appropriate for the particular tool based on certain physical characteristics of the particular tool. The selection of the appropriate relief pressure requires no operator intervention. Releasing the switch stops the pumping action immediately. Because the processes of connecting the tool filler port to the relief valve outlet, and determining whether the tool is completely filled, are identical to those employed with the widely-used traditional hand-operated pump, operators will quickly and naturally establish a xe2x80x9ccomfort levelxe2x80x9d of competence with the inventive pumping system.
In one embodiment, the invention is a relief valve for connecting to either of at least two tools or vessels. Each of the vessels has a different overpressure protection requirement and a distinctive pressure connector. The relief valve includes a body, an inlet, and a discharge outlet. A first pressure relief outlet provides the overpressure protection required by one of the vessels, while a second pressure relief outlet provides the overpressure protection required by the other of the vessels. A selector member, also known as a pressure insert, located in the body of the relief valve is actuated by one of the vessels"" pressure connectors and not the other vessel""s pressure connector when the relief valve""s discharge outlet is connected to the vessels, respectively. When actuated, the selector member or pressure insert blocks flow to the relief valve""s first pressure relief outlet or the second pressure relief outlet. The relief outlet that has the lowest pressure setpoint and is not blocked will open to protect the vessel.
The relief valve is equipped with a first spring-loaded piston and seat assembly that is adjusted to provide the overpressure protection requirement of one of the vessels. Another spring-loaded piston and seat assembly provides the overpressure protection requirement of the other of the vessels. The piston and seat assemblies are positioned between the inlet and the first and second pressure relief outlets, respectively. The selector member is actuated by a pressure connector having a protrusion inserted at least a predetermined distance into the discharge outlet.
In another embodiment, the invention is a relief valve for protecting two different batch application tools, each with a different pressure connector. The relief valve includes a body, an inlet, and a discharge outlet. Two separate pressure relief outlets provide the overpressure protection required by each of the tools, respectively. A pressure insert is actuated by one and only one of the tool""s pressure connectors when the discharge outlet is connected to the tools. Actuating the selector member blocks flow to one of the pressure relief outlets.
The relief valve may include a relief channel having a mouth that communicates with the body. The pressure connector actuates the selector member by forcing it away from the discharge outlet, so that the selector member covers the mouth. Preferably, the mouth is surrounded by a dam and the selector member includes a depression for receiving the dam when the selector member is actuated. The combination of the selector member and the dam stops any flow from passing through the lower pressure relief outlet until that particular tool is disconnected from the discharge outlet.
In still another embodiment, the invention is a pumping system for filling a variety of taper tools and drywall finishing tools. Each of the tools has one of two different overpressure protection requirements and a pressure connector that is indicative of the tool""s protection requirement. The pumping system includes a motor, a powered pump, and a selective relief valve, as described above.
The present invention offers a simple, portable and cost effective pumping system for the filling of batch application tools. Strain on operators is significantly reduced by the elimination of tiresome hand pumping. The pumping system unit is suitable for use with readily-available electrical current, is easily cleaned and requires minimal training to operate. It is capable of filling a wide range of tools without operator adjustment or danger of over-pressurization.